multi destination for "ip helper-address"?

[xiaoliangyue]

hi, Gangs,

on IOS, it seems only 1 destination is allowed for command "ip helper-address". How about if I deploy 2 DHCP servers in the network?

Thx,

Jon

[Jon Marshall]

Jon

"on IOS, it seems only 1 destination is allowed for command "ip helper-address"

Not sure where you get this impression from. You can configure multiple ip helper-addresses under a L3 interface. Not sure of the actual limit but i have used up to 4 in a transition period. Be aware that if you have multiple ip helpers the router/L3 switch will send a DHCP request on behalf of the client to all those listed.

Jon

[Leo Laohoo]

It is suppose to take multiple ip helper-address.

What is the version of IOS are you using?

[xiaoliangyue]

just tried on c3750, v12.2

SW(config-if)#ip helper-address 1.1.1.1 ?

SW(config-if)#ip helper-address 1.1.1.1,2.2.2.2 ?

% Unrecognized command

[Jon Marshall · Accepted solution]

You need to enter them as separate lines ie.

SW(config)# ip helper-address 1.1.1.1

SW(config)# ip helper-address 2.2.2.2

Jon

[xiaoliangyue]

Ah, I'm tooo stupid... Thanks, buddy!

[b.julin]

There is one caveat, which hopefully you won't run into. Certain devices like the ASA can get cranky if you have multiple DHCP servers load balancing. If they don't get a reply from the server their relay agent asked by unicast and get it from the peer instead, they'll drop it, even if you listed both the DHCP peers in the relay line.

We had to move our dial-in zones to only be served by a single server.